J. Engelfriet, "Attribute Grammars: Attribute Evaluation Methods", Methods and Tools in Compiler Construction, Cambridge University Press, 1984.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....structure is most suited for simultaneously decorating ffl Under which restrictions can parse graphs for attribute grammars be decorated ffl For which types of attribute grammars is it possible to give decorators that simultaneously evaluate the attribute values of all parses. ffl Similar to [Eng84a, Eng84b] it might be the case that in the case of simultaneously decorating multiple parses some sort of taxonomy does exist between the different classes of attribute grammars. To get answers on these question further research is necessary. The concepts of data flow graphs for parallel algorithms and ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, 1984.

....structure is most suited for simultaneously decorating ffl Under which restrictions can parse graphs for attribute grammars be decorated ffl For which types of attribute grammars is it possible to give decorators that simultaneously evaluate the attribute values of all parses. ffl Similar to [Eng84a, Eng84b] it might be the case that in the case of simultaneously decorating multiple parses some sort of taxonomy does exist between the different classes of attribute grammars. To get answers on these question further research is necessary. The concepts of data flow graphs for parallel algorithms and ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. Technical Report Memoranda Informatica 84-2, University of Twente, 1984.

....computable. 18 1.6.6 Computing the decoration We show here how we can compute a valid decoration bottom up, in a non deterministic way, if one exists. This is not the way it is usually done, but we need this for Chapter 2, where we will have a tree automaton simulate an attribute grammar. See [Eng84], but also [FV95] for the usual ways to compute decorations. Definition 1.36. Let Sigma be an operator alphabet, G a weakly non circular attribute grammar over Sigma and t a tree over Sigma. A top less decoration of t is a function dec assigning to every hff; ui 2 A(t) a value dec(hff; ui) 2 W ....

....With the help of Theorem 2.14 we can transform OE(x 1 ) to a node recognizing ag (G; ffi) with L(OE(x 1 ) L(G; ffi) or, in other words, t; u) j= OE(x 1 ) iff hffi; ui G;t = true. Since attribute evaluation takes linear time for a non circular attribute grammar with finite semantic domains [Eng84], it takes linear time to find all v such that (t; v) j= OE(x 1 ) Suppose k 1. Using Lemma 2.18 (with j = k Gamma 1) OE(x 1 ; x k ) can be transformed into an mso formula (x) over Sigma [ Sigma Theta B k Gamma1 ) with one free node variable, such that (t; u 1 ; u k ) j= ....

Joost Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, 1984. 99

....beyond the storage of the attribute values themselves, as the remainder of its state can be maintained in a few global variables. In our evaluator, we use an alternative implementation strategy in which visits are mapped onto ordinary subroutine calls in the target language of our implementation [18, 49]. An evaluation plan can be decomposed into a series of segments, each terminated by a SUSPEND instruction, and representing the actions to be performed upon the i th visit. We construct a set of visit procedures for each AST operator, one for each segment of the evaluation plan. For visit i, the ....

....function body depends not only upon the calling node s parent, but also upon which of the parent s children it happens to be. Techniques for solving this problem, which arises in the construction of demand driven evaluators for conventional AGs, are well known, and are described in Engelfriet [18] and Jourdan [41] These methods are awkward when rendered in a strongly typed object oriented target language, however. For this reason, we restrict functional attributes to be synthesized only. It is possible to achieve the effect of inherited functional attributes using objects, suggesting that ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, 1984.

....implementation, relying on inheritance and virtual methods. This paper shows how a demand driven evaluator can be implemented very conveniently in Java, also making use of Java s interface mechanism. 1 Introduction There is a large variety of algorithms for evaluation of Attribute Grammars (AGs) [2]. One particularly simple and general algorithm is the demand driven algorithm where each attribute is viewed as a function. To evaluate a particular attribute, its corresponding function is called, and this function will in turn call the functions corresponding to its dependent attributes, ....

....algorithm, e.g. Madsen [10] and a variety of different implementation styles have been proposed. The algorithm is also applicable to extended AG formalisms including non local connections, known as occurrence attributes or reference attributes [11, 5] In Engelfriet s survey of evaluation methods [2], the demand driven algorithm is referred to as P4 , and the optimal variant as P5 . Other descriptions of the algorithm includes Jalili s [6] Several researchers have showed how the algorithm lends itself to implementation in different kinds of languages: Jourdan gives an implementation in ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction, pp 103-137. Cambridge University Press, 1984.

....implementation for the class of absolutely noncircular attribute grammars[8] Katayama[7] translates attribute grammars into Pascal procedures. In his scheme attributes may be evaluated more than once, although he claims otherwise. An overview of these and other evaluation techniques is given in[3]. Deransart and Maluszynski[2] use attribute grammars to analyse logic programs. They derive conditions under which a Prolog program allows a nonstandard, but efficient, evaluation strategy. 13 Takeichi[12] obtains one touch algorithms by introducing higher order functions. The main conclusion ....

J. Engelfriet. Attribute grammars: attribute evaluation methods. In B. Lorho, editor, Methods and Tools For Compiler Construction, pages 103-- 138, Cambridge University Press, 1984.

.... ACC = ACC A(FA ( I) 1 Occurrences without controlling loops give rise to scalarwise singleton access patterns. IF FA ( I) 2 EA THEN ACC = ACC A 0 [oe A (F A ( I) ENDIF The identification of statements that can exploit sparsity is done by means of an attribute grammar [1, 17], based on a context free grammar for assignment statements. 2 The following semantic rules are used to associate the strongest condition , constructed from guards, with each expression in a synthesized attribute nz, to indicate when the value of this expression is nonzero, under the assumption ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, 1984.

....and intensional) attributes to be kept, or (which is the same) the (extensional and intensional) attributes to be discarded. We identified three possible solutions. ffl Last Sweep. The semantic evaluator generator analizes the semantic rules and determines the proper multi sweep strategy (see [8]) for evaluating intensional attributes. Making the hypothesis that the relevant attributes are those evaluated in the last sweep, the generated semantic evaluator produces a decorated document with attributes of the last sweep only. ffl Directives in the Semantic DTD. The designer of the SRD ....

....to obtain a general, although inefficient, semantic evaluator. Hence, more specialized evaluations methods are necessary to obtain fast semantic evaluation. In the literature, several methods have been proposed for AGs. The best known are the one sweep and multi sweep grammars, described in [8], and the ordered attribute grammars proposed in [13] We think that these methods can be adapted to the evaluation of SRDs; in particular, the adaptations should concern the way dependencies determined by different branches of conditional rules affect the evaluation strategy and the computation ....

J. Engelfriet. Attribute grammars: Attribute evaluation methods. In [19], 1984.

....the sequel we will restrict ourselves to top down parsing. On one hand, many different parsing techniques have been investigated (cf. 1] On the other hand, attribute evaluation algorithms are known, which coincide to differently powerful subclasses of the whole class of attribute grammars (cf. [10]) Now the question arises whether it is possible to interleave the two steps, i.e. to parse the given input string and to compute its semantic value simultaneously. The advantage of this combination is the possibility of saving storage space, because there is no need to keep the syntax tree in ....

....fact that, even if the underlying grammar is L attributed and hence, attribute dependencies are compatible with parsing, a function is computed for every node x of the parse tree rather than a value. Finally, the third technique applies to the class of pseudo L attribute grammars as defined in [10]. The attribute evaluation algorithm is based on a depth first left to right traversal over the syntax tree. With respect to the local attribute dependencies, it tries to evaluate as many attribute occurrences as possible. If the algorithm returns to a node y and it has computed the value of a ....

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Joost Engelfriet. Attribute Grammars: Attribute Evaluation Methods. In Bernard Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, 1984.

....Most of the research in the area has hence focused on the automatic production of eOEcient code without losing expressiveness. This has resulted in the identi cation of classes of AGs of various size and inherent eOEciency, and of characterization algorithms for each of these classes [DJL88, Eng84, Alb91] For reasons of eOEciency, these works on evaluation methods have mostly avoided to use higher order functions. 2 In this context, the problem of eliminating intermediate data structures introduced by function composition has been studied by Ganzinger and Giegerich and solved by their ....

....Jourdan Nil f N il;s Nil : s Nil = f n Cons a list f Cons;s Cons : s Cons = f c (a,s list ) Figure 7: The generic AG for list sense) and this, whatever way is used to resolve this system of equations. In other words, from a given speci cation (AG) dioeerent techniques [Eng84] can be used to generate an attribute evaluator, leading possibly to dioeerent evaluations methods but always to the same solution. So, the semantics of an AG is only based on its speci cation (the signatures of semantic rules) and is independent of the evaluation method. From the AG point of ....

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Joost Engelfriet. Attribute grammars: Attribute evaluation methods. In Bernard Lorho, editor, Methods and Tools for Compiler Construction, pages 103138. Cambridge University Press, New York, 1984.

.... example in [GG84, Joh87, PDRJ96] Nevertheless, AGs specifications have some important characteristics which allow them to be clear, concise and easily maintained [JPJ 90, JP92, Paa95] First they are declarative, i.e. program specification is completely independent of any evaluation order [Eng84] Secondly they allow a complex computation to be decomposed into small easily understandable local parts (on each constructor) which are joined together by the generator evaluator. Finally they make the structure (constructors) explicit in the specification, facilitating structure based ....

....derived from the constructors of this type and are valid for all accumulating functions of all fold programs defined on this type. Furthermore, the class of AGs which corresponds to functions expressed with folds is a well known (actually, the simplest) class of AGs, called purely synthesized [Eng84] and noted S 1 the 1 refers to the fact that each non terminal carries a single attribute (see also a translation from AGs to catamorphisms in [FJMM91] 2.3 Deforestation Since the folds and purely synthesized AGs expressiveness and evaluation methods are very similar, the aim of this ....

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Joost Engelfriet. Attribute grammars: Attribute evaluation methods. In Bernard Lorho, editor, Methods and Tools for Compiler Construction, pages 103--138. Cambridge University Press, New York, 1984.

....problem of inefficiency in terms of memory usage and CPU utilization, which can be solved by using a fine grain model. 2. 2 Attribute Grammars An attribute grammar (AG) is a context free grammar (CFG) augmented by attributes, functions defining values of attributes, and conditions over attributes [14, 21, 53]. An attribute grammar can be used to specify a translation of a language using attributes associated with syntactic components. This thesis treats scientific visualization as a translation from one data language to another and presents an AG based approach to building modules. Attribute grammars ....

Joost Engelfriet. Attribute grammars: Attribute evaluation methods. In B. Lorho, editor, Methods and Tools for Compiler Construction: An Advanced Course, pages 103--138. Cambridge University Press, Cambridge, England, 1984.

....generator is the most intricate and most important part of an Attribute Grammar system. However, as of today, the only evaluation method for which we have studied in detail the feasibility and correctness of the iplane shiftj technique described above is the visit sequence paradigm [Kas80, Eng84, Kas91] applicable to l ordered AGs and, with a very slight extension, to strongly non circular AGs [Par88] Other evaluation methods will be studied in a forthcoming paper. The visit sequence is our preferred method because: these evaluators reach the best compromise between the time and space ....

....produce complete evaluators from the ordered sequences, as outlined above. 3.1. 1 De nitions and preprocessing The de nitions of l ordered Attribute Grammars, TOPs, augmented dependency graphs and visit sequences, together with the construction of the latter from the formers, are quite classical [Eng84, Alb91] but we repeat them here for the sake of completeness and because we introduce ordered sequences which are easier to reason about than visit sequences. De nition 3.1 (l ordered Attribute Grammars et al. Let AG = G; A; F ) be a (classical) Attribute Grammar, with G = N; T; Z; P ) ....

Joost Engelfriet. Attribute grammars: Attribute evaluation methods. In Bernard Lorho, editor, Methods and Tools for Compiler Construction, pages 103138. Cambridge University Press, 1984.

....is de ned to be the unique 2 k for which there exist q 1 ; q k 2 Q such that q j 2 h ; ji for j 2 [1; k] and ( q 1 ; q k ) 2 h ; 0i. The set R(root) consists of the root rule h ; 0i = F . Clearly, G is noncircular. In fact, it is a two pass attribute grammar (cf. e.g. [Eng3]) in the rst pass over the input tree all values of can be computed bottom up, and in the second pass all values of and m can be computed top down. ut 6.2 Binary mso formulas It is shown in [BloEng] that a formula (x; y) 2 MSOL 2 ( can be computed by a tree walking automaton. A ....

J. Engelfriet; Attribute grammars: attribute evaluation methods, in Methods and Tools for Compiler Construction (B. Lorho, ed.), Cambridge University Press, 1984, 103-138

....in terms of attribute grammars, one of the best known formal models for defining syntax directed semantics. Of course, attribute grammars are still a specification language, but they are much closer to implementation than mso logic, and their implementation has been studied extensively (see, e.g. [DerJouLor, Eng3, KuhVog2]) To be precise, we prove that a tree transduction is mso definable iff it can be computed by an attributed tree transducer with look ahead (att R for short) This is a transducer which consists of two attribute grammars, each computing a tree transduction, the composition of which is the ....

....u, X) U , and (y) v. As a very simple example, g; u; v) j= path(x; y) means that there is a path from u to v in g, and g j= 8x; y(path(x; y) means that g is strongly connected. 2. 3 Attribute Grammars In this subsection we recall some terminology concerning attribute grammars (see, e.g. [Knu, DerJouLor, Eng3, KuhVog2]) In order to allow the attribute grammar to work on arbitrary trees over an operator alphabet, rather than on derivation trees of an underlying context free grammar, we consider a slight variation of the attribute grammar that was introduced in [Ful] The semantic rules of the attribute grammar ....

J. Engelfriet; Attribute grammars: attribute evaluation methods, in Methods and Tools for Compiler Construction (B. Lorho, ed.), Cambridge University Press, 1984, 103--138

....such a restriction attribute grammars can compute arbitrary node properties. Note also that properly speaking, attribute grammars are still a specification language, but they are certainly closer to implementation than mso logic, and their implementation has been studied extensively (see, e.g. [DerJouLor, Eng2]) Since the attributes of a tree can be evaluated in linear time (in the size of the tree) our second result implies that mso definable node properties can be computed in linear time and that mso definable binary node relations can be computed in quadratic time, and, in general, mso definable ....

....MSO Node Properties In this section we show our second main result: a node property can be defined by an mso formula iff it can be computed by an attribute grammar of which all attributes have finitely many values. We start by recalling some terminology concerning attribute grammars (see, e.g. [Knu, DerJouLor, Eng2]) Then we define the so called node selecting attribute grammar, which computes a property of the nodes of the input tree, and show that these attribute grammars compute exactly the mso definable node properties. Finally, we define the concept of an attributed relabeling of the nodes of a tree, ....

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J. Engelfriet; Attribute grammars: attribute evaluation methods, in Methods and Tools for Compiler Construction (ed. B. Lorho), Cambridge University Press, 1984, 103--138

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J. Engelfriet, "Attribute Grammars: Attribute Evaluation Methods", Methods and Tools in Compiler Construction, Cambridge University Press, 1984.

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